I use TotalMD. I don't know if it's the most seamless but it has worked fine for us for 10+ years. We bought the desktop version of TotalMD at the beginning and have done several upgrades thru the years. I send the e-claims to the paid Availity clearninghouse. I pay for the extra Advanced Claims Editing feature which I CANNOT live without. (Can explain more if you're interested but basically you create your own claim scrubs). The Avality part has been $213 per month for the whole time I've used them.

Serene
Office Manager
General Pediatrics
Houston, Texas